Implement vload_half{,n} and vload(half)

v2: add vload(half) as well
    make helpers amdgpu specific (NVPTX uses different private AS numbering)
    use clang builtin on clang >= 6

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Reviewed-by: Tom Stellard <tstellar@redhat.com>
llvm-svn: 312839
diff --git a/libclc/amdgpu/lib/SOURCES_4.0 b/libclc/amdgpu/lib/SOURCES_4.0
index 5851798..69c5e5c 100644
--- a/libclc/amdgpu/lib/SOURCES_4.0
+++ b/libclc/amdgpu/lib/SOURCES_4.0
@@ -1 +1,2 @@
+shared/vload_half_helpers.ll
 shared/vstore_half_helpers.ll